In the first pic above, your detector has the words “with voice” printed on it. Unless there’s a new version, the zcombo doesn’t have voice alerts.

However, first alert does manufacture other models of smoke and CO detectors with a wireless interconnect capability that uses a proprietary protocol, not z-wave. And those detectors do have voice alerts.

So are you sure you purchased a first alert device with a z-wave radio in it? Obviously it won’t pair with ST if it doesn’t have that.

The First Alert ZCOMBO-G is a z-wave protocol smoke and carbon monoxide combination alarm. This battery operated alarm will operate with 3Rd party, certified z-wave Devices enabled with the First Aler ...